Virtually all buildings and enclosures where human activity takes place require venting of one type or another. The type of venting device employed will depend upon the kind of enclosure to be vented. For example, bathrooms containing showers typically have active vents with fans to vent steam to the outdoors. Kitchens, particularly in restaurants and hotels, similarly have powered vents for removing smoke and steam to the outdoors. By contrast, other types of enclosures, such as attics, do not require active venting.
In previous years, building codes in various jurisdictions frequently allowed for the venting of bathroom and kitchen gases to the attic of a building, which gases would then be vented to the outdoors through an attic vent. However, in recent years, many building codes have begun to require that such gases be actively vented directly to the outdoors through a dedicated vent. Typically, such gases would be actively vented into a conduit, which conduit is operatively connected to a vent duct. The vent duct is in turn connected to the exhaust outlet of the vent. The size of the conduit will vary according to the source of the vented gases. For example, dryer conduits are typically 5-inch diameter hoses. By contrast, bathroom conduits are typically 4-inch diameter hoses.
The desired location of the exhaust outlet of such a vent will depend on the location of the room being actively vented. Under some circumstances, it may be convenient or even necessary for the exhaust outlet to be located on the soffit of the building, that is, a substantially horizontal surface located underneath a roof overhang. It is often desirable to have the exhaust outlet on a soffit, because doing so is more cost effective than having to make a hole in a roof or wall for mounting an exhaust outlet.
In order to conserve energy, it is desirable to construct the vent so that cold air from the outdoors may not flow into the building through the exhaust outlet of the vent. While such back flow could not take place while air is being forcibly exhausted out through the vent, most active vents only operate intermittently, and back flow is possible when they are off.
A variety of venting devices are currently known. For example, U.S. Pat. No. 5,791,985 issued to Schiedegger et al. discloses a modular soffit vent including a rectangular base member having a planar securing flange and a large circular opening. Welded to the base member is a length of vent duct communicating with the circular opening. The vent duct has an adapter which allows for the attachment of different-sized conduits. A circular air-permeable screen fits into the circular opening, and a cage-like cover fits over the entire rectangular base member, thus preventing debris, animals and the like from entering the vent.
This device suffers from the problem of being complex to install in a soffit because it comprises many separate external pieces such as the cover, base member and screen. Also, the duct is rigidly connected to the base member. Therefore, if the base member requires replacement, the duct must be replaced as well, thus increasing replacement costs. Since the base member is mounted on the exterior of the building, it is likely to corrode or decay faster than the duct, and would therefore likely require replacement more often. Finally, this device does not address the problem of back flow of air through the vent.
U.S. Pat. No. 5,167,578 discloses a soffit vent which includes an air inlet in a room to be vented, communicating through a duct to a housing having an air flow passage, the housing being mounted on the external side of a soffit. The housing includes a flange for mounting the housing on the soffit. Mounted within the housing on the external side of the flange is a flap valve which is normally closed by gravity. When air flow through the vent is commenced by the operation of a power-driven unit in the interior of the building, the flap valve is lifted by the air flow, allowing the vented air to be exhausted. When the power-driven air flow ceases, the flap valve falls closed, thus preventing external air from flowing back into the building. The flap valve disclosed in this patent is hinged at its upper edge, and hangs closed when air flow is absent. Because of the structure of this device, the flapper valve must be mounted outside of the soffit in a position where the air flow past the valve is substantially horizontal. Since the soffit itself is typically substantially horizontal, the housing must protrude from the soffit in order for the vent to operate. The result is a vent which, when installed, must protrude in an unsightly fashion from the soffit. Furthermore, the housing may be difficult and expensive to manufacture, because of the relatively complex three-dimensional shape that the housing must take on in order to carry the flap valve in the appropriate position.
U.S. Pat. No. 5,722,181 discloses an exhaust vent. The device includes an air exit aperture and a vent frame adapted to establish communication with the air exit aperture, and a plurality of flow control louvers mounted so as to permit exiting air flow while blocking back flow. The device also includes a hood and cage mounted outside the louvers. The louvers are hinged at their top ends so as to be hanging vertically when air flow is present, and pushed open toward a horizontal position when air is exhausted through the vent. Each of the louvers hangs by its upper edge, and the louvers are mounted outside the vent frame on the exterior of the building.
As a result of this structure, the device is not suitable for use on a horizontal soffit, as the louvers would hang open even when no air is being exhausted through the vent. Also, the device disclosed would necessarily produce an unsightly protrusion from the soffit by virtue of the hood and cage mounted on the outside of the louvers.
U.S. Pat. Nos. 2,344,789; 2,218,348; and 4,151,789 also disclose venting devices have flap-style valves to prevent back flow from the external environment, but, for similar reasons, none of these devices is suitable for mounting on a soffit.